1. Field of the Invention
This invention relates generally to the field of plastic containers and closures therefor, and more specifically to a threaded finish for a nonremovable closure that is more material efficient than the predecessor technology.
2. Description of the Related Technology
Plastic containers that are manufactured from a material such as polyethylene terephthalate (PET) using the well-known reheat stretch blow molding process typically include a threaded finish portion that has at least one helical thread for receiving a closure, such as a closure cap or a dispensing closure.
One type of a conventional finish portion 10 for a plastic container that is specifically designed to resist removal of a closure from the container by a consumer is shown in FIG. 1. Finish portion 10 includes a threaded portion 12 that has a helical thread 14 and a flat or horizontal thread 16 positioned beneath the helical thread 14. The helical thread 14 and the horizontal thread 16 are configured so that the helical thread 14 merges into the horizontal thread 16. As a result, the threads of a closure that is twisted on to the finish portion 10 will first be guided by the helical thread 14 and then snapped downward over the flat or horizontal thread 16 into a position where it will be difficult for a consumer to remove the closure from the container. Such a closure configuration is commonly referred to as a nonremovable closure.
The finish portion 10 of the container that is shown in FIG. 1 further includes a transfer bead 18 and a shape to define a gripping indentation 20 between the transfer bead 18 and the threaded portion 12. The purpose of the transfer bead 18 and the gripping indentation 20 is to facilitate automated robotic handling of the container during the container manufacturing process and the filling process.
The gripping indentation 20 of the conventional container that is shown in FIG. 1 has a shape that is substantially square when viewed in longitudinal cross-section because of the presence of a prominent ledge 22 having an outer substantially vertical sidewall 24 between the gripping indentation 20 and the transfer bead 18. While such containers have been used effectively for their intended purposes the present inventors have determined that the inclusion of the prominent ledge 22 is not necessary in order to facilitate handling of the container. The inclusion of the prominent ledge 22 accordingly requires unnecessary additional plastic material that makes the conventional design suboptimal in terms of its material efficiency and environmental suitability. A need exists for an improved finish configuration for a nonremovable closure that is more material efficient and environmentally sound than that of the predecessor technology.